1. Global Winds
It’s all about the open system, our atmosphere, trying to restore equilibrium, balance!!
Obi-wan, I feel a disturbance in the force!!

2. For this reason, it’s warmer near the equator than at the poles.
Climatic Variation & Seasons on Earth
Uneven heating of Earth’s surface causes predictable latitudinal variation
in climate. Why? - Angle of incidence… equator vs. poles
North Pole
Equator
Earth
South Pole
Thus, radiation is more intense near the equator compared to the poles.
For this reason, it’s warmer near the equator than at the poles.

3. Earth North Pole Equator South Pole Earth’s Seasons
Tilt of the Earth’s axis towards or away from the sun creates the seasons
When the north pole tilts toward the sun, it gets more radiation – more warmth
during the summer
SUMMER (Northern Hemisphere)
North Pole
Equator
Earth
When the north pole tilts toward the sun, the south pole tilts away
So when it’s summer in the north,
it’s winter in the south
South Pole
WINTER (Southern Hemisphere)

4. Earth North Pole Equator South Pole Earth’s Seasons
Tilt of the Earth’s axis towards or away from the sun creates the seasons
WINTER (Northern Hemisphere)
When the north pole tilts away
from the sun, it gets less radiation –
So it’s colder during the winter
North Pole
Equator
Earth
South Pole
When the north pole tilts away from the sun, the south pole tilts toward it…
When it’s winter in the north,
it’s summer in the south
SUMMER (Southern Hemisphere)

5. Intense radiation at the equator warms the air
Air cools as it rises, moisture condenses and falls as rain
Warm air rises, collecting moisture
Lots of rain in the tropics!

6. some of the rising air flows north some of the rising air flows south
Rising air is now dry…
some of the rising air flows north
some of the rising air flows south
Dry air descends at around 30º N
…and at around
30º S
Deserts
Deserts
The descending air flows N and S

7. What causes global wind patterns?
Uneven heating of the earth causes
less dense hot air to rise at equator = low pressure
More dense cold air to sink at poles = high pressure
Air moves from high P (poles) to low P (equator)

8. Paper strips activity

9. Non-Rotating Earth Model
• On a hypothetical non-rotating planet with a smooth surface of either all land or all water, two large thermally produced cells would form.

10. Circulation on a Non-Rotating Earth
Makes no sense without caption in book

11. Rotation of earth activity
Pen and paper activity

12. Rotating Earth Model
• If other effects were added to the global circulation model, the two-cell convection system would break down into smaller cells.

13. Global Winds!

14. Circulation on a Rotating Earth
Makes no sense without caption in book

15. WIND BELTS
Trade winds are two belts of winds that blow almost constantly from easterly directions and are located on the north and south sides of the subtropical highs.
Westerlies are the dominant west-to-east motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highs.

16. WIND BELTS
Polar easterlies are winds that blow from the polar high toward the subpolar low. These winds are not constant like the trade winds.
A polar front is a stormy frontal zone separating cold air masses of polar origin from warm air masses of tropical origin.

17. Make note of the location of borders of the convection cells.
Interesting stuff happens at the boundaries between convection cells….. A Closer Look
60o
Make note of the location of borders of the convection cells.
30o

18. There are 3 Main Climate Zones

19. Analyzing Evidence
60o N and S latitude mark the border between the temperate regions and the polar regions.
It also marks the border between the
300 N and S latitude mark the border between the temperate regions and the tropical region.
So…

20. Explanation So when the warm air rises at equator.
As it approaches 30o N & S latitude some of the air must be cooling down so sinks.

21. Continued
When its closer to the surface, the surface absorbs a lot of the sun’s energy so the air must warm up again and rises.

22. Continued
Then when the air approaches 60o N & S latitude the some air cools down and so sinks again.

23. 6 Convection Cells
So we end up with 3 convection cells in each hemisphere.

24. What else is going on at the boundaries between convection cells ?
Air rises, low pressure at
Equator
60 N and S
RESULT – can be cloudy, rainy weather
Air sinks, high pressure at
Poles
30 N and S
RESULT – fair, nice weather

25. At 30 N and S…. up high – subtropical jetstream
At surface – weak winds known as the horse latitudes
Weird?? Why ‘horse latitudes’?

26. At 60 N and S…. At equator…. At surface, weak winds - doldrums
Up high – POLAR JET STREAM !!!
At equator….
At surface, weak winds - doldrums

27. Jet Stream
High velocity Polar and subtropical jet stream winds are located in the lower tropopause
Polar jet stream travels at mph, ~ 4-7 miles up, 1-3 miles thick and mi wide
HUGE!!!

28. Two jets in each hemisphere
Polar jet is stronger, lower
Sub tropical jet is weaker, higher up

29. How does the jetstream affect our weather patterns?
It controls how much polar air drops into the mid latitudes and how much mid-latitude air moves into the northern, polar areas.
It moves with the seasons, more south in the winter and more north in the summer.

30. What are the other factors that affect the global wind patterns?
besides Coriolis effect?

31. Land vs sea worksheet

32. Global Winds Influenced by Continents
• The only truly continuous pressure belt is the subpolar low in the Southern Hemisphere. In the Northern Hemisphere, where land masses break up the ocean surface, large seasonal temperature differences disrupt the pressure pattern.

33. Global Winds Influenced by Continents
• Monsoons are the seasonal reversal of wind direction associated with large continents, especially Asia. In winter, the wind blows from land to sea. In summer, the wind blows from sea to land.

34. We just learned this !!! 
The difference is that at the Jersey Shore the land and sea breezes change according to __________ and ________
In Asia the land and sea breezes change according to _____________ and __________

35. Monsoon Photos
Click here to learn more about monsoons…

36. Who needs this information?
What occupations, etc.?
Why?

37. Thinking back to people who need global wind info ….
Why do meteorologists need the info?
What is the difference between weather and climate???
Do global winds affect weather or climate?

38. There are 3 Main Climate Zones

39. “Air Pressure & Wind”
High
&
Low
Pressures

40. Pressure Centers and Winds
Cyclones are centers
of low pressure.
(storms occur here)
Anticyclones are
centers of high
pressure.
 In cyclones, the pressure decreases from the outer isobars toward the center. In anticyclones, just the opposite is the case—the values of the isobars increase from the outside toward the center.

41. How are weather maps made?
In cyclones, (L) the pressure decreases from the outer isobars toward the center.
In anticyclones, (H) just the opposite is the case—the values of the isobars increase from the outside toward the center.

42. Pressure Differences
Low Pressure system air coming up either cloud cover and precipitation or no clouds because no moisture
High pressure system air coming down generally fair skies

43. H Wind and Pressure Relationships L
950 mb.
970 mb.
960 mb.
930 mb. H L
WINDS ALWAYS MOVE FROM HIGH PRESSURE AREAS TO LOW PRESSURE AREAS!!!!!!!

44. Cyclonic and Anticyclonic Winds
• When the pressure gradient and the Coriolis effect are applied to pressure centers in the Northern Hemisphere, winds blow:
Counterclockwise around a low pressure area
Clockwise around a high pressure area

45. Cyclonic and Anticyclonic Winds
Makes no sense without caption in book

46. Pressure Centers and Winds
 Weather and Air Pressure
• Rising air is associated with cloud formation and precipitation, whereas sinking air produces clear skies.
 Weather Forecasting
• Weather reports emphasize the locations and possible paths of cyclones and anticyclones.
• Low-pressure centers can produce bad weather in any season.

47. Identify the Wind Belts
Makes no sense without caption in book
Click on the link below to see the wind belts in action and answer some questions!